If you go back far enough, everything lived in the sea. At various
points in evolutionary history, enterprising individuals within many
different animal groups moved out onto the land, sometimes even to the
most parched deserts, taking their own private seawater with them in
blood and cellular fluids. In addition to the reptiles, birds, mammals
and insects which we see all around us, other groups that have succeeded
out of water include scorpions, snails, crustaceans such as woodlice
and land crabs, millipedes and centipedes, spiders and various worms.
And we mustn’t forget the plants, without whose prior invasion of the
land none of the other migrations could have happened.

Moving from water to land involved a major redesign of every aspect
of life, including breathing and reproduction. Nevertheless, a good
number of thoroughgoing land animals later turned around, abandoned
their hard-earned terrestrial re-tooling, and returned to the Water
Seals have only gone part way back. They show us what the intermediates
might have been like, on the way to extreme cases such as whales and
dugongs. Whales (including the small whales we call dolphins) and
dugongs, with their close cousins the manatees, ceased to be land
creatures altogether and reverted to the full marine habits of their
remote ancestors. They don‘t even come ashore to breed. They do,
however, still breathe air, having never developed anything equivalent
to the gills of their earlier marine incarnation. Turtles went back to
the sea a very long time ago and, like all vertebrate returnees to the
water, they breathe air. However, they are, in one respect, less fully
given back to the water than whales or dugongs, for turtles still lay
their eggs on beaches.

There is evidence that all modem turtles are descended from a
terrestrial ancestor which lived before most of the dinosaurs. There are
two key fossils called Progaochelys quenstedtiand
Palaeochersis talampayensis dating from early dinosaur times, which
appear to be close to the ancestry of all modem turtles and tortoises.
You might wonder how we can tell whether fossil animals lived on land or
in water, especially if only fragments are found. Sometimes it`s
obvious. Ichthyosarus were reptilian contemporaries of the dinosaurs,
with fins and streamlined bodies. The fossils look like dolphins and
they surely lived like dolphins, in the water. With turtles it is a
little less obvious. One way to tell is by measuring the bones of their
forelimbs.

Walter Joyce and Jacques Gauthier, at Yale University, obtained
three measurements in these particular bones of 71 species of living
turtles and tortoises. They used a kind of triangular graph paper to
plot the three measurements against one another. All the land tortoise
species formed a tight cluster of points in the upper part of the
triangle; all the water turtles cluster in the lower part of the
triangular graph. There was no overlap, except when they added some
species that spend time both in water and on land. Sure enough, these
amphibious species show up on the triangular graph approximately half
way between the ‘wet cluster' of sea turtles and the ‘dry cluster' of
land tortoises. 'The next step was to determine where the fossil fell.
The bones of P quenstedti and P. talampayensis leave
us in no doubt. Their points on the graph are right in the thick of the
dry cluster. Both these fossils were dry-land tortoises. They come from
the era before our turtles returned to the water.

You might think, therefore, that modem land tortoises have probably
stayed on land ever since those early terrestrial times, as most
mammals did after a few of them went back to the sea. But apparently
not. If you draw out the family tree of all modern turtles and
tortoises, nearly all the branches are aquatic. Today’s land tortoises
constitute a single branch, deeply nested among branches consisting of
aquatic turtles. This suggests that modern land tortoises have not
stayed on land continuously since the time of P. quenstedti and P. talampayensis.
Rather, their ancestors were among those who went back to the water,
and they then re-emerged back onto the land in (relatively) more recent
times.

Tortoises therefore represent a remarkable double return. In common
with all mammals, reptiles and binds, their remote ancestors were marine
fish and before that various more or less worm-like creatures
stretching back, still in the sea, to the primeval bacteria. Later
ancestors lived on land and stayed there for a very large number of
generations. Later ancestors still evolved back into the water and
became sea turtles. And finally they returned yet again to the land as
tortoises, some of which now live in the driest of deserts.

Questions 27-30

Answer the questions below
Choose NO MORE THAN TWO WORDS from the passage for each answer
Write your answers in boxes 27-30 on your answer sheet.

27. What had to transfer from sea to land before any animals could migrate?
28. Which TWO processes are mentioned as those in which animals had to make big changes as they moved onto land?
29. Which physical feature. possessed by their ancestors, do whales lack?
30. Which animals might ichthyosaurs have resembled?

Questions 31-33
Do the following statements agree with the information given in Reading Passage 54?
In boxes 31-33 on your answer sheet, write

TRUE if the statement agrees with the informationFALSEif the statement contradicts the informationNOT GIVEN if there is no information on this more than once.

31.Turtles were among the first group of animals to migrate back to the sea.
32.It is always difficult to determine where an animal lived when its fossilized remains are incomplete.
33.The habitat of ichthyosaurs can be determined by the appearance of their fossilized remains.

Questions 34-39
Complete the flow-chart below

Choose NO MORE THAN TWO WORDS AND/OR A NUMBER from the passage for each answer.

Write your answers in boxes 34-39 on your answer sheet.

Method of determining where the ancestors of turtles and tortoises come from

Step 1: 71 species of living turtles and tortoises were examined and a total of 34 ................were taken from the bones of their forelimbs.Step 2: The data was recorded on a 35 ................... (necessary for comparing the information). Outcome: Land tortoises were represented by a dense 36 .................. of points towards the top. Sea turtles were grouped together in the bottom part.Step 3: The same data was collected from some living 37
.................. species and added to the other results. Outcome: The
points for these species turned out to be positioned about 38 .................. up the triangle between the land tortoises and the sea turtles.Step 4: Bones of R quenstedti and P talampayensis were examined in a similar way and the results added.
Outcome: The position of the points indicated that both these ancient creatures were39......................

Questions 40Choose the correct letter A, B, C or D.
Write the correct letter in box 40 on your answer sheet.
According to the writer, the most significant thing about tortoises is that

A they are able to adapt to life in extremely dry environments.
B their original life form was a kind of primeval bacteria,
C they have so much in common with sea turtles.
D they have made the transition from sea to land more than once.

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